This invention relates to a water jacket arrangement for a marine two cycle internal combustion engine and more particularly to an improved cooling system for an internal combustion engine.
In water cooled internal combustion engines, it is the normal practice to provide a separate cooling jacket for the cylinder head and cylinder block. With V type engines, each cylinder head and each bank of the cylinder block normally has its own cooling jacket. It is conventionally the practice to pass the cold cooling water first through the cylinder block cooling jacket and then through the cylinder head cooling jacket. This arrangement, however, has several disadvantages.
In the first instance, the cylinder head normally has the higher heat loading associated with it and when the cooling water is first circulated through the cylinder block, there is not as great a differential between the temperature of the cooling water and the cylinder head. Cooling efficiency is therefore diminished. Furthermore, if the engine is operated on the two stroke crankcase compression principle, as is common with may liquid cooled engines, then the cold cooling water is also in proximity to the scavenge passages of the cylinder block and tends to quench them. This will cause condensation of the fuel in the fuel/air mixture that is transferred from the crankcase to the combustion chambers through these scavenge passageways. Accordingly, poor running conditions will result.
The aforenoted problems are particularly acute in conjunction with marine propulsion engines. These engines normally receive cooling water from the body of water in which they are operating, circulate it through the cooling jackets and then return it back to the body of water. As a result, the inlet water tends to be at a lower temperature than engines having closed cooling systems and employing a heat exchanger. Hence, the aforenoted problems are particularly acute with marine propulsion engines.
It is, therefore, a principal object of this invention to provide an improved cooling arrangement for an internal combustion engine.
It is a further object of this invention to provide a cooling system for an internal combustion engine wherein the cylinder block and cylinder head will each receive adequate degrees of cooling.
It is a still further object of this invention to provide an improved cooling system for a two cycle crankcase compression type of internal combustion engine.
It is a yet further object of this invention to provide an improved cooling system for a marine propulsion engine.